Ion source



K. WEIMER May 27, 1958 ION SOURCE Filed Jan. 6, 1956 7 5 7 2 6 I m 2 a I2 l h A I 80 3 I 2 w Z 3 a 8 m iii; llll ll Tr. m m r lg 2 Inventor?KARL WE/MER 7 O v m :5 mm 2 .64 I n. w 2 :1. I I2 "a I I xr/xu/ 6 I w 9z a k x v l all I 0 F I1- be 5 w W E I Affameys United States Patent2,836,750 ION SOURCE Karl Weimer, Gottingen, Germany, assignor toLicentia- Patent-Verwaltungs G. m. b. 1%., Hamburg, Germany ApplicationJanuary 6, 1956, Serial No. 557,773 Claims priority, application GermanyJanuary 7, 1955 12 Claims. (Cl. 313-63) This invention relates to an ionsource. It relates more particularly to a novel type of an ion sourcefor ionizing gaseous particles.

It is already known in the art to ionize gaseous particles by means ofelectrons, for instance, those generated by the high frequency field ofa high frequency coil or emitted from a cathode.

In order to achieve a pressure difference between the ionization chamberof the ion source and a space provided for accelerating the ions, thehitherto known sources require a narrow channel between the ionizationchamber and the above mentioned space, which channel reduces the yieldof the ionic source by restricting the beam of the ionic particles.

it is an object of my invention to provide a new ion source with a highyield.

This object is achieved in the ion source according to my inventionwhich source is characterized by the ionization of a stream of gaseousparticles travelling in an evacuated chamber with a high and preferablysupersonic velocity.

According to a further feature of my invention 1 provide, in an ionsource, a Laval nozzle capable of producing a jet of gaseous particlesof supersonic speed.

According to yet another feature of the invention I provide for anadjustment of a gaseous stream in an ion source in such a manner as tocause the development of standing shock waves in said gaseous beam.Thereby I attain the formation of wave nodes in the gaseous beam whichfact permits an effective ionization of the gaseous particles in thenodes of the standing shock waves.

The high density of gaseous particles in the supersonic jet and, inparticular, due to the formation of a standing shock wave, in the nodesof the latter, facilitates ionization of the particles, and consequentlyleads to a higher yield of ionized particles than can be attained withthe known devices.

in a preferred embodiment of the invention as hereinafter more fullydescribed, the ion source comprises an evacuated chamber to whichpumping means are connected. A stream of gaseous particles is introducedinto this evacuated chamber as a supersonic jet. In the chamber, thegaseous particles are ionized preferably in a node of a standing shockwave formed by the supersonic jet and separated from the remainingunionized gaseous stream.

The ionized particles are guided to outlet means, which may, forinstance, be connected to known means for the separation of isotopes.

It is preferred to provide magnetic fields to separate the ionizedparticles from the gaseous beam.

in a further preferred embodiment, electric fields are provided forseparating the ionized particles from the gaseous beam.

In a particularly advantageous embodiment of the invention, the streamof gaseous particles is introduced with supersonic velocity into thechamber of the ion source and directed on to an opening for pumpingmeans, so that a high vacuum is maintained in the chamber and thegaseous beam is concentrated to occupy only a small part of the chamber.

The injection of gaseous particles at supersonic speed into a chamber,for instance through a Laval nozzle,

limits the width of the gaseous particle jet, since the velocitycomponent of the particles in the direction of the jet is greater thanthe component transverse to said jet, which latter component depends onthe diffusion velocity of the gaseous particles over the entire volumeof the chamber.

In the known devices, in which gas is caused to flow into an ionizationchamber by means of a smaller pressure difference corresponding to aparticle velocity below the speed of sound, the pressure prevailing inthe chamber is practically uniform.

The supersonic injection of gaseous particles according to the inventionoffers the important advantage that the conventionally required specialmeans for the restriction of particle flow in the ionization chamberand/ or a subsequent acceleration of the ionized particles in theisotope separator can be dispensed with.

The ion source according to my invention permits to attain a much higheryield of ionized particles than the known ion sources, and,nevertheless, practically eliminates the undesirable penetration ofunionized particles into that part of the device through which theionized particles are emitted from the source.

The aforesaid objects and advantages will be better understood at thehand of the detailed description following hereinafter in connectionwith Figures 1 and 2 of the accompanying drawings wherein Figure l is aschematic sectional view of an ion source according to the inventionprovided with a supersonic jet nozzle and a high frequency coil andother accessories according to the invention.

Figure 2 is another schematic sectional view provided with an electrongun for ionizing the gaseous particles which are introduced into theevacuated chamber with supersonic velocity.

Referring now to the drawings it will be seen that the ion sourcecomprises an evacuated chamber 1 having a supersonic jet nozzle,preferably a Laval nozzle, 2. A stream 3 of gaseous particles enters theevacuated chamber 1 with supersonic velocity through the supersonic jetnozzle 2. The stream 3 of gaseous particles is provided from a stockbottle (not shown), which is connected with supersonic jet nozzle 2 bymeans of a pipe and a throttle (not shown). According to its highvelocity the beam 3 of gaseous particles remains concentrated over arelatively long distance. An opening 4 is provided in the evacuatedchamber 1 which opening is located opposite the opening 4 which latteris connected via a pipe 7 to a pump 5. Hollow vessels 18 combined withthe wall parts 6 of the chamber 1 and the part 7:: of the pipe 7 betweenthe opening 4 and the pump 5 are preferably provided for containingcooling media so that a high vacuum in the chamber it is maintained.Between the wall parts 6 and the adjacent wall parts so of the chamber1, on the one hand, between pipe parts 7a and the remaining part of pipe7 leading to the pump 5, intermediate pieces 12 are arranged fortherrnic insulation.

As an example in the Figures 1 and 2 an adjustment of the gaseous beamis shown which leads to the formation of shock waves resembling astanding wave.

In order to obtain a high rate of ionization the ionizing means arearranged in the neighborhood of a node 8 of particle stream 3. Forinstance in Figure 1 a high frequency coil 9, and in Figure 2 anelectron beam 15, are provided for ionization. The electron beam 15' isgenerated by an electron source 16 and directed through a node 8 on to atarget 17 which latter is at a desired potential.

The beam 13 of ionized particles is separated from the beam 3 of gaseousparticles by means of a magnetic field and preferably guided by the samefield through 'too narrow'an opening 10. This advantage can preferablybe achieved by ionizing gaseous particles in a concentrated gaseousbeamin such a manner that already in those parts of the chamber 1 adiacentto the opening 10, a relatively high vacuum is maintained.

It will be understood that this invention is susceptible to modificationin order to adapt itto different usages and conditions, and,accordingly, it is desired to comprehend such modifications within thisinvention as may fall Withinthe scope'of the appended claims.

I claim: 3 1

l. Inan ion source comprising an evacuated chamber, pumping meansconnected with said evacuated chamber, means for introducing a stream ofgaseousparticles in said evacuated chamber at supersonic speed, meansfor ionizing a portion of said gaseous particles, means for separatingthe ionized portion of said particles from said stream of gaseousparticles, and outlet means for said ionized particles.

2. In an ion source comprising an evacuated chamber, pumping meansconnected with said evacuated chamber, jet producing means forintroducing a stream of gaseous particles in said evacuated chamber,which stream leaves said jet producing means with supersonic velocityand develops a standing shock wave in said chamber, means for ionizing aportion of said particles, means for sepa rating the ionized particlesfrom" said stream of gaseous particles, and outlet means for saidionized particles.

7 3. In an ion source comprising an evacuated chamber, jet producingmeans for introducing a stream of gaseous particles in said evacuatedchamber, which stream leaves jet'with supersonic velocity, means forionizing a portion of said particles, means for separating the ionizedparticles from said stream of gaseous particles, pumping means forremoving said gaseous particles from said evacuated chamber, saidevacuated chamber havingan opening opposite said jet producing means, towhich opening said pumping means are connected, whereby said stream ofgaseous particles is directed toward said'opening, and

outlet means for said ionized particles.

4. In an ion' source comprising anevacuated chamber,

.jet producing means for introducing a stream of gaseous particles insaid evacuated chamber, said stream leaving said jet producing meanswith supersonic velocity, means for ionizing a portion of saidparticles, means for separating the ionized particles from said streamof gaseous particlesppumping means for removing the remaining gaseousparticles fromsaid evacuated chamber, the open- 7 ing for said'pumpingmeans being arranged opposite to said jet producing means, cooling meansarranged adiacent to said opening for. said pumping means, and outletmeans for said ionized particles, disposed at an angle to said streamofgaseous particles. g V

5. In an ion source comprising an evacuated chamber, pumping meansconnected withisaid evacuated chamber,

' means for introducing a stream of gaseous particles with supersonicvelocity into said evacuated chamber so as to form a standing shock wavetherein, means for ionizing a portion of said particles, said ionizingmeans being arranged so that the ionization of said gaseous particlestakes place inat least one nodeof said standing shock Wave of gaseousparticles, means for separating the ionized particles from said streamof gaseous particles, and outlet means for said ionized. particles.

, 6. In an ion sourcccomprising an evacuated chamber.

pumping means connected with said evacuated chamber,

means for introducing a stream of gaseous particles with pumping meansconnected with said evacuated chamber, means for introducing a stream ofgaseous particlesvvith supersonic velocity in said evacuated chamber,high fro-- quen'cy coil means, said gaseous particles traversing saidhigh frequency coil means and a portion of said particles being ionizedby the high frequency field of said high frequency coil means, means forseparating the ionized particles from said stream of gaseous particles,and outlet means for said'ionized particles. I I

V 8. In an ion source comprising an evacuated'chamber, pumpingmeans'connected with said evacuated chamber, means for introducing astream of gaseous particles with supersonic velocity in said evacuatedchamber, means for generating and accelerating electrons, said electronsbeing directed onto said stream of gaseous particles for ionizing aportion of said gaseous particles, means for separating the ionizedparticles from said stream of gaseous particles, and outlet means forsaid ionized particles.

9. In an ion source comprising an evacuated chamber, pumping meansconnected With said evacuated chamber, means for introducing a stream ofgaseous particles with supersonic velocity in said evacuated chamber,means for ionizing a portion. of said particles, electric means" forseparating the ionized particles from said stream of gaseous particles,and outlet means for said ionized particles. p I a 10, In an ion sourcecomprising an evacuated chamber,

pumping means connected with said evacuated chamber,

means for introducing a stream of gaseous particles with supersonicvelocity in said evacuated chamber, means for ionizing aportion of saidparticles, magnetic means for separating the ionized particles from saidstream of gase- 1 ous particles, and outlet means for said ionizedparticles; 11. In an ion source comprising an evacuated chamber, pumpingmeans connected With'said evacuated chamber,

means for introducinga stream of gaseous particles with supersonicvelocity in said evacuated chamber, meansfor ionizing a portion of saidparticles, means for separating the ionized particles from said streamof gaseous particles, and outlet meansfor said ionized particles, saidoutlet means being connected with means for separation of isotopes. g V

12. In an ion sourcecomprising-an evacuated chamber .a Laval nozzle forintroducing a stream of gaseous particles with supersonic velocity intosaid evacuated'cham- .ber'in order, to develop a standing shock wavehaving at least one node therein, said chamber having an openingopposite said Laval jet, pumping means connected with said opening, saidstream of gaseous particles being concentrated to. occupy only a smallpart of said chamber and being directed toward said opening, means forioniz- 7 ing a portion of said particles and comprising a high frequencycoil disposed in the region of a nodeof said shock Wave, said coil beingadapted to generate a high frequency field which ionizes said gaseousparticles in said node, magnetic means for separating the ionizedparticles from said stream of gaseous particles, and outlet means forsaid ionized particles, saidoutlet means being disposed substantially ata right angle to the direction of said stream of gaseous particles fromsaid Laval nozzle to said opening, and permitting an unobstructed flowof said ionized particles from said chamber to the outside ReferencesCited in the file of this patent UNITED STATES PATENTS 2,400,557 LawlorMa 21, 1946 2,582,215 Koppius Jan; 15,1952 2,633,539

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